A variety of pumps are known currently for pumping liquids, wastewater, and other liquids containing solids such as garbage, disposable products, woven fabrics, poly-materials, and other items. While these pumps can chop solids to varying degrees to permit solids to flow through to the output of the pump for disposal, other problems occur because modern wastewater contains solids in the form of synthetic disposable products and woven fibrous materials. Conventional pump designs do a poor job of shredding such solids and woven fibrous materials.
In order to process solids conventional pumps generally employ a non-clog style impeller design to suck the solids into the pump. When solids are woven fibrous materials, these solids are not sheared into a passable sized solid by the non-clog style impeller when initially entering the pump. Typically, woven fibrous materials become balled around the eye of the impeller due to the water and impeller rotation. Once balled, woven fibrous materials often fail to pass out of the pump, reduce the pump output flow, and can result in pump failure such as, for example, clogging, seizing and motor burnout.
Conventional chop or chopper pump designs typically use a centrifugal pump equipped with a cutting system to facilitate the chopping and maceration action of solids that are present in the pumped liquid, whereby a drive unit (e.g. electric motor, hydraulic motor, etc.) turns an impeller and the cutting system. The impeller is fixedly mounted to a drive shaft of the drive unit. When such solids enter the inlet, the impeller has sharpened shroud edges adapted for cutting the solids against spiral grooves in a back plate. Chopper pumps are available in various configurations and are typically equipped with an electric motor to run the impeller and provide torque for the chopping system. Existing chopper pump designs have disadvantages in processing solids of woven fibrous materials including clogging, wrapping or stoppage of the pump operation because once the solids have entered the impeller, these solids must travel across to the back plate before the cutting action, whereby wrapping can occur before cutting. It would be an improvement over conventional chopper pump designs to prevent clogging of the pump itself and of the adjacent piping by such solids and woven fibrous materials.
In conventional grinder pump designs the impeller or grinder is positioned at the intake portion of the pump so as to use the impeller as part of the cutting mechanism. Existing grinder pump designs have disadvantages including not allowing solids to gain entry until sliced into smaller particles, i.e. in an all-or-nothing action relying on the solids being cut or kicked-out before being sucked back to the impeller for another try. The kick-out action of solids and woven fibrous materials in conventional grinder pump designs is often unsuccessful and less than optimal. Wrapping and clogging can still occur even after multiple kick-out actions of the solids because woven fibrous materials accumulate to eventually clog the pump intake that can leading to pump failure (e.g. burnout). A common solution is to use higher capacity pumps with larger motors and intake openings (i.e., increase in the size of the pump) in order to allow passage of solids a relatively large diameter intake. However, over-sizing the pump to increase pump intake also results in a cost increase in the pump needed for the application.
Consequently there is a long-felt need for an cost effective, optimally-sized pump configured to overcome the numerous problems associated with woven fibrous materials and other disadvantages of the prior art. The present invention provides a durable centrifugal pump effective for pumping solids and woven fibrous materials suspended in a liquid in an effective smaller pump design. The shear and shred pump design of the present invention reduces clogging and failures in the operation of cutting, shearing, or shredding of solids, and especially woven fibrous materials, present at the pump intake. The shear and shred pump design of the present invention also provides an improved centrifugal pump in a smaller design where a larger pumps heretofore have been used. Consequently, there is a long-felt need for a pump having an improved cutting action for use in applications where a smaller design is suitable to process modern wastewater and in other liquid processing applications.